Salt-containing seabed tunnel hole slag fluidized solidified soil and preparation method and application thereof

Abstract

The present application relates to the technical field of low-carbon cement-based building materials, and particularly relates to a salt-containing seabed tunnel hole slag fluidized solidified soil, the salt-containing seabed tunnel hole slag is modified, the sulfate and the chloride salt in the hole slag are pre-solidified, and a low-sulfur high-calcium type raw material system is prepared by cooperating with a cementitious material and an additive, the fluidized solidified soil has the characteristics of high fluidity and high mechanical strength.

Description

Technical Field

[0001] This invention relates to the field of low-carbon cement-based building materials technology, and in particular to a fluidized solidified soil for saline-containing submarine tunnel slag, its preparation method, and its application. Background Technology

[0002] With the rapid development of subsea tunnels, coastal tunnels, and cross-sea projects, a large amount of saline tunnel muck is generated during shield tunneling and tunnel construction. This type of muck typically contains high concentrations of soluble salt ions, including sodium (Na₂O₃). + Mg 2+ Ca 2+ Cations and Cl - SO4 2- Currently, the saline tunnel debris, containing anions, has not yet been utilized as a resource.

[0003] Studies have shown that tunnel muck without salt ions, after crushing and screening, can be used as coarse aggregate, fine aggregate, or filler in the preparation of mortar, concrete, and other building materials, and has been widely applied. However, the migration of salts in tunnel muck containing salt ions within the solidified body may lead to environmental risks such as salt return crystallization, pore structure deterioration, and leachate salt release, restricting the large-scale engineering utilization of salt-containing tunnel muck. Sea sand also contains soluble salt ions, but its characteristics differ from those of seabed tunnel muck. Salt ions in sea sand are easily dissolved and removed; however, the gradual release of sulfates and chlorides from seabed tunnel muck also restricts its use as a building material.

[0004] The prior art CN119735387A discloses a process for processing submarine tunnel slag aggregate. The process involves soaking the submarine tunnel slag aggregate in a barium hydroxide solution to solidify sulfate ions, then soaking it in a sodium silicate solution to fix the barium sulfate precipitate, and finally soaking it in an ethyl cellulose solution and an ion-exchange chitosan sol solution. After that, it can be used as coarse aggregate for concrete preparation. However, the above process is relatively complex and costly.

[0005] Fluidized solidified soil is formed by solidifying soil, silt, slag, and solid waste with cementitious materials. Due to its good fluidity and certain mechanical strength, it is widely used in backfilling and filling engineering construction. Existing fluidized solidified soil technology is mainly designed for ordinary soil or low-salt environments. Its cementing system, admixture system, and rheological control methods are all based on a low-ion interference environment. Existing technology CN120081630A discloses a fluidized solidified soil prepared using engineering slag. It uses engineering slag, fly ash, slag powder, cement, alkali activator, water-reducing agent, defoamer, and water as component A, and adds a network structure formed by in-situ cross-linking polymerization of water-soluble polymers to improve the density of the solidified body. It can effectively prevent the intrusion of corrosive substances in seawater, so it can be used in marine environments. However, when fluidized solidified soil is prepared directly using saline slag, problems such as a sharp decrease in fluidity, uncontrolled setting time, early false setting, discontinuous strength development, and long-term durability deterioration are likely to occur, which seriously affect the construction adaptability and engineering safety.

[0006] Therefore, there is an urgent need for a high-performance fluidized solidified soil preparation method that can achieve stable fluid properties, controllable solidification, and continuous strength development in a high-salt ion environment. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a fluidized solidified soil for saline-containing seabed tunnel slag. Specifically, this invention modifies the saline-containing seabed tunnel slag, pre-solidifies the sulfates and chlorides in the slag, and prepares a low-sulfur, high-calcium raw material system in combination with cementing materials and additives. The fluidized solidified soil has high fluidity and high mechanical strength characteristics.

[0008] The present invention relates to a fluidized solidified soil for saline submarine tunnel slag, which is composed of the following raw materials in parts by weight: 100-120 parts cement, 80-100 parts mineral powder, 40-50 parts fly ash, 30-40 parts calcium carbide slag, 1000-1200 parts modified slag, 5-10 parts water-reducing agent, 8-10 parts sodium hexametaphosphate, 5-9 parts sodium polyacrylate, 1-3 parts air-entraining agent, and appropriate amount of water.

[0009] The modified tunnel slag preparation process is as follows: 100 parts of salt-containing submarine tunnel slag, 6-10 parts of sintered red mud, 2-4 parts of quicklime, 0.5-1 parts of sodium citrate, and 80-100 parts of water are mixed evenly, aged and dried to obtain the final product.

[0010] Unlike ordinary tunnel muck, submarine tunnel muck contains soluble inorganic salts, which exist in the micropores of the muck particles. These soluble inorganic salts will gradually release sulfate and chloride ions, posing structural risks to construction. Most notably, sulfate ions slowly form ettringite in the hardened solidified soil, causing expansion and cracking, while chloride ions can lead to the risk of steel reinforcement corrosion. Studies have shown that the hydration of cement-based materials can produce products such as AFt, AFm, CSH, CAH, and CH. Chloride ions can participate in the hydration reaction to generate Friedel salts, which are then converted to Kuzel salts with the participation of sulfate ions. However, the formation of Kuzel salts leads to the release of chloride ions, increasing the content of soluble chloride ions in the system. To solve the above problems, this invention first involves aging saline submarine tunnel slag with sintered red mud, quicklime, and sodium citrate after adding water. Studies have shown that sintered red mud contains a large amount of C3A and C2S. In a high-concentration CH environment, combined with sodium citrate, it can continuously capture chloride and sulfate ions in saline submarine tunnel slag. The low-sulfur, high-calcium environment is conducive to inhibiting the conversion of Friedel salts to Kuzel salts. After aging, this invention can significantly reduce the content of soluble chloride ions and allow sulfate ions to participate in pre-hydration in advance, avoiding the expansion and cracking of the hardened soil in the later stage and ensuring that the mechanical properties of the hardened soil do not shrink in the later stage.

[0011] This invention uses cement, mineral powder, fly ash, and carbide slag as cementing materials. A large amount of mineral powder and fly ash are used to replace cement, and carbide slag is added as an activator. The water-reducing agent can break the flocculation structure of the cementing material. Sodium hexametaphosphate and sodium polyacrylate can improve the dispersibility of modified cave slag particles. In order to improve the fluidity of the soil solidified by adding modified cave slag, this invention adds a portion of air-entraining agent to form microbubbles to achieve particle lubrication without producing slurry. The cementing material system is also designed as "high calcium and low sulfur" to ensure the effective solidification of soluble chloride ion content in the solidified soil.

[0012] Preferably, the modified tunnel slag has a particle size of 0-4.25 mm. More preferably, the modified tunnel slag has a particle size of 0.01-4.25 mm. Even more preferably, the modified tunnel slag has a particle size of 0.075-4.25 mm. The soil particles in fluidized solidified soil generally fall into the category of fine particles. Coarse aggregates larger than 5 mm can easily lead to poor workability of the solidified soil slurry. Therefore, if the particle size of the tunnel slag from the subsea tunnel is large, it needs to be crushed and / or screened.

[0013] Preferably, the cement is at least one of silicate cement and ordinary silicate cement. More preferably, the cement is at least one of grade 42.5 and grade 52.5.

[0014] Preferably, the mineral powder is at least one of S95 grade and S105 grade.

[0015] Preferably, the fly ash is at least one of secondary fly ash and primary fly ash.

[0016] Preferably, the aging and fermentation time is 3-10 days.

[0017] Preferably, the drying process is selected from at least one of oven drying and air drying. Drying is performed in this invention for ease of weighing and measurement; however, drying may not be necessary. During use, the moisture content is calculated, and then converted. The water contained in the modified slag should be deducted from the amount of water added in the preparation of the solidified soil.

[0018] Preferably, the water-reducing agent is at least one of polycarboxylate water-reducing agent, naphthalene-based water-reducing agent, and aliphatic water-reducing agent.

[0019] Preferably, the air-entraining agent is at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and saponin.

[0020] Preferably, the water-to-solid ratio is 0.45-0.52.

[0021] The present invention also relates to a method for preparing the above-mentioned salt-containing submarine tunnel slag fluidized solidified soil, specifically including the following steps: mixing the raw materials evenly to obtain the final product.

[0022] A preferred method for preparing fluidized solidified soil for saline-containing submarine tunnel slag includes the following steps:

[0023] 1) Weigh each raw material according to its weight proportions.

[0024] 2) Mix cement, mineral powder, fly ash, and carbide slag evenly to obtain a composite cementitious material.

[0025] 3) Mix the water-reducing agent, air-entraining agent, and water evenly to obtain a liquid mixture.

[0026] 4) Mix the composite cementitious material, modified slag, sodium hexametaphosphate, and sodium polyacrylate evenly to obtain a powder.

[0027] 5) Mix the powder and liquid materials evenly to obtain the final product.

[0028] This invention also relates to the application of the above-mentioned fluidized solidified soil for saline submarine tunnel slag in backfilling construction.

[0029] This invention has the following technical advantages:

[0030] 1. This invention pretreats saline-containing submarine tunnel excavation material to reduce its soluble chloride ion content, thereby avoiding its impact on the flowability and mechanical properties of the solidified soil and enabling efficient utilization of saline-containing submarine tunnel excavation material.

[0031] 2. The modified slag of this invention, after aging and curing, produces some pre-hydrated products, which can promote bonding with cementitious materials and increase the mechanical properties of the fluidized solidified soil.

[0032] 3. This invention uses a large amount of industrial solid waste to replace cement as a cementing material, which reduces costs and makes use of waste. The fluidized solidified soil has a high content of slag and a low content of cementing material. The preparation process is simple and it has good fluidity and mechanical properties. Detailed Implementation

[0033] To characterize the technical effect of the present invention, the salt-containing submarine tunnel slag was first modified, and the soluble chloride ion content was detected in accordance with JGJ / T322.

[0034] Blank example

[0035] The saline-containing seabed tunnel debris, after testing, had a free chloride ion content of 0.66‰.

[0036] Preparation Example 1

[0037] Mix 100 parts of saline submarine tunnel slag, 10 parts of sintered red mud, 3 parts of quicklime, 0.9 parts of sodium citrate, and 100 parts of water evenly, let the mixture age for 7 days, and then dry it to obtain the final product. Testing showed that its free chloride ion content was 0.02‰.

[0038] Preparation Example 2

[0039] Mix 100 parts of saline submarine tunnel slag, 8 parts of sintered red mud, 4 parts of quicklime, 0.7 parts of sodium citrate, and 100 parts of water evenly, let the mixture age, and then dry it to obtain the final product. Testing showed that its free chloride ion content was 0.03‰.

[0040] Compare with Example 1

[0041] Mix 100 parts of saline submarine tunnel slag, 10 parts of mineral powder, 3 parts of dihydrate gypsum, 0.9 parts of sodium citrate, and 100 parts of water evenly, let it age for 7 days, and then dry it to obtain the final product. Testing showed that its free chloride ion content was 0.27‰.

[0042] Compare with Example 2

[0043] Mix 100 parts of saline submarine tunnel slag, 10 parts of Bayer red mud, 3 parts of water glass, 0.9 parts of sodium citrate, and 100 parts of water evenly, let it age for 7 days, and then dry it to obtain the final product. Testing showed that its free chloride ion content was 0.33‰.

[0044] Compare with Example 3

[0045] Mix 100 parts of saline submarine tunnel slag, 10 parts of sintered red mud, 3 parts of quicklime, and 100 parts of water evenly, let it age for 7 days, and then dry it to obtain the final product. Testing showed that its free chloride ion content was 0.12‰.

[0046] After pretreatment, the free chloride ion content of the modified slag decreased significantly, meeting the standard of GB55008 for sand used in reinforced concrete. Fluidized solidified soil was prepared, and its fluidity and mechanical properties were tested. For fluidity testing, an acrylic cylinder with a height and diameter of 80 mm was used as the container. After the slurry flowed out, the diameter was measured. Mechanical properties were tested according to GB / T50123 for unconfined compressive strength. The cement used was P·O42.5 cement, the mineral powder was S95 grade, the fly ash was grade II fly ash, the water-reducing agent was polycarboxylate superplasticizer with a water reduction rate of 26%, and the air-entraining agent was sodium dodecylbenzene sulfonate.

[0047] Example 1

[0048] The fluidized solidified soil is composed of the following raw materials in parts by weight: 120 parts cement, 80 parts mineral powder, 45 parts fly ash, 38 parts carbide slag, 1150 parts slag from the preparation example 1, 9 parts water-reducing agent, 10 parts sodium hexametaphosphate, 6 parts sodium polyacrylate, 2 parts air-entraining agent, and a water-to-solid ratio of 0.5.

[0049] The fluidity of the solidified soil was measured to be 240 mm, the unconfined compressive strength at 14 days was 2.5 MPa, and the unconfined compressive strength at 28 days was 4.6 MPa.

[0050] Example 2

[0051] The fluidized solidified soil is composed of the following raw materials in parts by weight: 110 parts cement, 90 parts mineral powder, 49 parts fly ash, 34 parts carbide slag, 1150 parts slag from the preparation example 1, 8 parts water-reducing agent, 8 parts sodium hexametaphosphate, 9 parts sodium polyacrylate, 2 parts air-entraining agent, and a water-to-solid ratio of 0.5.

[0052] The fluidity of the solidified soil was measured to be 235 mm, the 14-day unconfined compressive strength was 2.3 MPa, and the 28-day unconfined compressive strength was 4.2 MPa.

[0053] Comparative Example 1

[0054] The fluidized solidified soil is composed of the following raw materials in parts by weight: 120 parts cement, 80 parts mineral powder, 45 parts fly ash, 38 parts carbide slag, 1150 parts slag, 9 parts water-reducing agent, 10 parts sodium hexametaphosphate, 6 parts sodium polyacrylate, 2 parts air-entraining agent, and a water-to-solid ratio of 0.5.

[0055] The fluidity of the solidified soil was measured to be 120 mm, the unconfined compressive strength at 14 days was 0.7 MPa, and the unconfined compressive strength at 28 days was 1.9 MPa.

[0056] Comparative Example 2

[0057] The fluidized solidified soil is composed of the following raw materials in parts by weight: 120 parts cement, 80 parts mineral powder, 45 parts fly ash, 38 parts carbide slag, 1150 parts slag from the tunnel in control example 1, 9 parts water-reducing agent, 10 parts sodium hexametaphosphate, 6 parts sodium polyacrylate, 2 parts air-entraining agent, and a water-to-solid ratio of 0.5.

[0058] The fluidity of the solidified soil was measured to be 190 mm, the unconfined compressive strength at 14 days was 1.8 MPa, and the unconfined compressive strength at 28 days was 2.7 MPa.

[0059] Comparative Example 3

[0060] The fluidized solidified soil is composed of the following raw materials in parts by weight: 120 parts cement, 80 parts mineral powder, 45 parts fly ash, 38 parts carbide slag, 1150 parts slag from the tunnel in control example 2, 9 parts water-reducing agent, 10 parts sodium hexametaphosphate, 6 parts sodium polyacrylate, 2 parts air-entraining agent, and a water-to-solid ratio of 0.5.

[0061] The fluidity of the solidified soil was measured to be 175 mm, the unconfined compressive strength at 14 days was 1.4 MPa, and the unconfined compressive strength at 28 days was 2.3 MPa.

[0062] Comparative Example 4

[0063] The fluidized solidified soil is composed of the following raw materials in parts by weight: 120 parts cement, 80 parts mineral powder, 45 parts fly ash, 38 parts carbide slag, 1150 parts slag from the tunnel of control example 3, 9 parts water-reducing agent, 10 parts sodium hexametaphosphate, 6 parts sodium polyacrylate, 2 parts air-entraining agent, and a water-to-solid ratio of 0.5.

[0064] The fluidity of the solidified soil was measured to be 200 mm, the unconfined compressive strength at 14 days was 1.9 MPa, and the unconfined compressive strength at 28 days was 2.6 MPa.

[0065] Comparative Example 5

[0066] The fluidized solidified soil is composed of the following raw materials in parts by weight: 120 parts cement, 100 parts mineral powder, 55 parts fly ash, 8 parts gypsum dihydrate, 1150 parts slag from the prepared example 1, 9 parts water-reducing agent, 10 parts sodium hexametaphosphate, 6 parts sodium polyacrylate, 2 parts air-entraining agent, and a water-to-solid ratio of 0.5.

[0067] The fluidity of the solidified soil was measured to be 195 mm, the unconfined compressive strength at 14 days was 2.4 MPa, and the unconfined compressive strength at 28 days was 3.4 MPa.

[0068] Comparative Example 6

[0069] The fluidized solidified soil is composed of the following raw materials in parts by weight: 120 parts cement, 80 parts mineral powder, 45 parts fly ash, 38 parts carbide slag, 1150 parts slag from the preparation example 1, 10 parts water-reducing agent, 10 parts sodium hexametaphosphate, 6 parts sodium polyacrylate, and a water-to-solid ratio of 0.5.

[0070] The fluidity of the solidified soil was measured to be 175 mm, the unconfined compressive strength at 14 days was 2.2 MPa, and the unconfined compressive strength at 28 days was 3.9 MPa.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fluidized solidified soil for saline-containing submarine tunnel slag, characterized in that, It is composed of the following raw materials in parts by weight: cement 100-120 parts, mineral powder 80-100 parts, fly ash 40-50 parts, calcium carbide slag 30-40 parts, modified slag 1000-1200 parts, water-reducing agent 5-10 parts, sodium hexametaphosphate 8-10 parts, sodium polyacrylate 5-9 parts, air-entraining agent 1-3 parts, and water as needed. The modified tunnel slag preparation process is as follows: 100 parts of saline submarine tunnel slag, 6-10 parts of sintered red mud, 2-4 parts of quicklime, 0.5-1 parts of sodium citrate, and 80-100 parts of water are mixed evenly, aged and dried to obtain the final product.

2. The fluidized solidified soil for saline-containing submarine tunnel slag as described in claim 1, characterized in that, The cement is at least one of silicate cement and ordinary silicate cement.

3. The fluidized solidified soil for saline-containing submarine tunnel slag as described in claim 1, characterized in that, The mineral powder is at least one of S95 grade and S105 grade.

4. The fluidized solidified soil for saline-containing submarine tunnel slag as described in claim 1, characterized in that, The fly ash is at least one of secondary fly ash and primary fly ash.

5. The fluidized solidified soil for saline-containing submarine tunnel slag as described in claim 1, characterized in that, The aging and fermentation time is 3-10 days, and the drying process is selected from at least one of oven drying and air drying.

6. The fluidized solidified soil for saline-containing submarine tunnel slag as described in claim 5, characterized in that, The water-reducing agent is at least one of polycarboxylate water-reducing agents, naphthalene-based water-reducing agents, and aliphatic water-reducing agents.

7. The fluidized solidified soil for saline-containing submarine tunnel slag as described in claim 1, characterized in that, The air-entraining agent is at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and saponins.

8. The fluidized solidified soil for saline-containing submarine tunnel slag as described in claim 1, characterized in that, The water-to-solid ratio is 0.45-0.

52.

9. The method for preparing the fluidized solidified soil for saline-containing submarine tunnel muck according to any one of claims 1-8, characterized in that, The process includes the following steps: mixing all the raw materials evenly to obtain the final product.

10. The application of the fluidized solidified soil for saline-containing submarine tunnel slag as described in any one of claims 1-8 in backfilling construction.